The present invention relates generally to backpacks and, more particularly, to backpacks having lift straps coupled to the shoulder straps.
Referring to FIG. 1, most conventional backpacks 10 have a pair of shoulder strap assemblies 28 and a waist strap 42 coupled to a storage compartment 34 for holding objects to be carried upon the back of a user. The shoulder strap assemblies 28 and the waist strap 42 distribute the load of the objects carried within the storage compartment 34 upon the shoulders and waist or hips of the user. Although backpacks arranged as described are effective in assisting a user in carrying objects upon the user""s back, they are not without problems. For instance, it was found that the ability to adjust the ratio of weight borne by the shoulders relative to the waist of the user was desirable. To accomplish this function, conventional backpacks have incorporated a pair of lift strap assemblies 12 which interconnect an upper portion 36 of the backpack 10 to the shoulder strap assemblies 28. By tightening the lift strap assemblies 12, a higher percentage of the load carried by the backpack 10 is borne by the waist strap 42. In contrast, by loosening the lift strap assemblies 12, a higher percentage of the load carried by the backpack 10 is carried by the shoulder strap assemblies 28.
Focusing now on the left lift strap assembly 12, a first end 20 of the lift strap 18 is rigidly affixed to the shoulder strap assembly 28 by stitching 24. The lift strap 18 then engages a buckle 16 attached to the upper portion 36 of the storage compartment 34 by a short anchor strap 14 at attachment location 26. The lift strap 18 is engaged with the buckle 16 by passing the second free end 22 of the lift strap 18 around at least one friction bar 44. The friction created by the change of direction of the lift strap 18 as the lift strap 18 encircles the friction bar 44 impedes the movement of the lift strap assembly 12 relative to the buckle until the buckle 16 is manipulated by the user.
To tighten the lift strap assembly 12, a user must raise his/her hand up above his/her head to grasp the free end 22 of the lift strap 18. Upon grasping the lift strap 18, the free end of the lift strap is forcefully pulled outward and away from the buckle 16. The force required to xe2x80x9cshortenxe2x80x9d the lift strap assembly 12 is substantial since the force exerted upon the free end 22 of the lift strap 18 must overcome any load on the lift strap 18 and all friction forces created by the engagement of the lift strap 18 with the friction bar 44 of the buckle 16. The harder one pulls of the lift strap, the greater the load placed upon the friction bar 44, and thus the greater the friction force that must be overcome to tighten the lift strap 18.
To xe2x80x9clengthenxe2x80x9d the lift strap assembly 12, a user must reach up and above the user""s head and grasp the buckle 16. The buckle 16 is then rotated to manipulate the angle which the lift strap 18 enters and exits the buckle to partially disengage the lift strap 18 from the friction bar 44, to permit the lift strap 18 to pass through the buckle 16, to lengthen the lift strap assembly 12.
Although conventional backpacks having lift straps may be effective, they are not without problems. For instance, to shorten the lift strap assembly 12, the user must exert a substantial force upon the free end 22 of the lift strap 18. This force must be sufficiently high to overcome any load on the lift strap 18 and the friction forces exerted by the friction bar 44 as discussed above, which may result in a strain or injury to the user. Further, the shortening of the lift strap assembly 12 in the manner described above may lead to the over tightening of the lift straps 18 which may result in shoulder and chest pain if tightened to an extreme. Further still, the buckle 16 is placed in a location obscured, or at least partially obscured, from sight; therefore buckle adjustment by the user is awkward, time consuming, and potentially injury causing as the user contorts his/her body to try to view the buckle.
Many of the same disadvantages are realized when a user desires to lengthen the lift strap assembly 12. More specifically, a user must again reach up and to the side of his/her head to obtain access to the buckle 16. Further, the act of reaching up and above one""s head may cause a loss of the user""s balance, resulting in a fall. This is especially true when a user is wearing a large, heavily loaded backpack. Even further, if the buckle 16 cannot be viewed by twisting one""s head around, manipulation of the buckle 16 must occur without visual reference, thereby making the proper operation of the buckle 16 difficult. Further still, some user""s may find the physical act of reaching up above one""s head difficult or impossible, especially for those having reduced mobility.
Therefore, there exists a need for a backpack having lift straps that are easy to operate, require less force to adjust, reduce the potential for over tightening, may be adjusted by a means that is easily viewed and accessed by the user, and satisfies the performance expectations of the user.
In accordance with one embodiment of the present invention, a backpack including a storage compartment and a shoulder strap assembly attached at a first end to the storage compartment at a first location and coupled at a second end to the storage compartment at a second location spaced from the first location is provided. The backpack further includes a buckle attached to the shoulder strap assembly and a lift strap having a first end attached to the upper portion of the storage compartment and spanning above the shoulder strap assembly from its location of attachment to the storage compartment to engagement with the buckle. The buckle is operable to selectively adjust the length of the lift strap to vary the proportion of the weight of the backpack supported by the shoulder strap assembly when engaged by the shoulders of a user wearing the backpack.
In accordance with further aspects of one embodiment of the present invention, the lift strap includes a second end extending beyond the buckle, wherein the buckle is operable to selectively adjust the length of the lift strap through manipulation of the second end of the lift strap. In accordance with still further aspects of one embodiment of the present invention, the buckle is actuatable between a first position, wherein the buckle prevents lift strap movement through the buckle in a first direction, and a second position, wherein the buckle permits movement of the lift strap through the buckle in the first direction. In accordance with yet still further aspects of one embodiment of the present invention, the buckle is actuatable between the first and the second positions through manipulation of a second end of the lift strap extending beyond the buckle. For instance, thebuckle may be actuatable from the first position to the second position by increasing the angle of inclination of the second end of the lift strap relative to the buckle. Or, the buckle may be actuatable from the second position to the first position by changing the angle that the second end of the lift strap extends from the buckle.
In accordance with other aspects of one embodiment of the present invention, the buckle is actuatable between a first position, wherein the buckle impedes lift strap movement through the buckle in a first direction for lengthening the lift strap, but permits lift strap movement through the buckle in a second direction opposite the first direction for shortening the lift strap, and a second position, wherein the buckle permits movement of the lift strap through the buckle in the first direction for lengthening the lift strap. In accordance with still other aspects of one embodiment of the present invention, the buckle includes a cam rotatable between a first position, wherein the cam impedes lift strap movement through the buckle in a first direction, and a second position, wherein the cam permits movement of the lift strap through the buckle in the first direction. The cam may be biased to assume the first position by an elastic member. The cam may engage the lift strap in the first position and at least partially disengage from the lift strap in the second position.
In accordance with yet still other aspects of one embodiment of the present invention, the backpack may further include a second shoulder strap assembly attached at a first end to the storage compartment at a first location and coupled at a second end to the storage compartment at a second location spaced from the first location and a second buckle attached to the second shoulder strap assembly. The backpack may also include a second lift strap having a first end attached to the upper portion of the storage compartment and spanning above the second shoulder strap assembly from its location of attachment to the storage compartment to engagement with the second buckle. The second buckle may be operable to selectively adjust the length of the second lift strap to vary the proportion of the weight of the backpack supported by the second shoulder strap assembly when engaged by the shoulders of a user wearing the backpack.
In accordance with additional aspects of one embodiment of the present invention, the backpack may further include a waist strap coupled to the lower portion of the storage compartment and operable to at least partially encircle the waist of a user. Further, the adjustment of the length of the lift strap may selectively adjust the ratio of weight carried by the shoulder strap assembly relative to the waist strap when the backpack is worn by a user. In accordance with further additional aspects of one embodiment of the present invention, the lift strap passes substantially straight through the buckle without undergoing a substantially change in direction.